This multicenter prospective controlled clinical trial will evaluate the emergency department (ED) use of Tc99m-sestamibi scanning to aid ED triage of patients presenting with symptoms suggestive of acute cardiac ischemia (ACI) who have normal or non-diagnostic electrocardiograms (ECGs). The trial's primary aim will be to assess the impact of sestamibi scanning on ED triage decisions: the degree to which those ED patients with ACI are hospitalized and those without ACI are not hospitalized. It's secondary aim will be to assess the impact of this use of sestamibi scanning on actual hospital costs.